Apparatus for electroslag-remelting of metals, in particular, steel

ABSTRACT

Apparatus for heating steel ingots produced in an electroslagremelting process. An electrode consisting of a steel of predetermined composition is remelted in an electroslag-remelting process. A slag composition is stored in a water-cooled mold and the electrode is inserted into this slag composition and an electric current is passed through the electrode thereby melting it. The molten metal settles in the mold and solidifies therein. A base plate supports the ingot formed by the solidification of the molten metal in the mold while the distance between the top of the slag layer and the top of the molten metal remains constant by increasing the distance between the mold and the base plate, thereby causing the solidified metal to exit from the mold as a solidified metal ingot. Means are provided for heating the exposed surfaces of the metal ingots exiting from their molds.

United States Patent [191 Schneidhofer [451 Apr. 16, 1974 APPARATUS FOR ELECTROSLAG-REMELTING OF METALS, IN PARTICULAR, STEEL [76] Inventor: Adolf Schneidhofer, Hermann Lonsgasse 27, 8605 Kapfenberg, Austria [22] Filed: June 19, 1972 21 Appl. No.: 264,309

' Related Application Data [62] Division of Ser. No. 72,783, Sept. 16, 1970,

abandoned.

[30] Foreign Application Priority Data Primary Examiner-J. Spencer Overholser Assistant Examiner-John E. Roethel [5 7] ABSTRACT Apparatus for heating steel ingots produced in an electroslag-remelting process. An electrode consisting of a steel of predetermined composition is remelted in an electroslag-remelting process. A slag composition is stored in a water-cooled mold and the electrode is inserted into this'slag composition and an electric current is passed through the electrode thereby melting it. The molten metal settles in the mold and solidifies therein. A base plate supports the ingot formed by the solidification of the molten metal in the mold while the distance between the top of the slag layer and the top of the molten metal remains constant by increasing the distance between the mold and the base plate, thereby causing the solidified metal to exit from the mold as a solidified metal ingot. Means are provided for heating the exposed surfaces of the metal ingots exiting from their molds.

2 Claims, 3 Drawing Figures PATENTEDAPR 16 19M SHEET 1 BF 2 Fig. 1

PATENTEUAPR 16 1974 Sam 2 OF 2 Fig.3

APPARATUS FOR ELECTROSLAG-REMELTING OF METALS, IN PARTICULAR, STEEL This is a division of application Ser. No. 72,783 filed on Sept. 16, I970, now abandoned.

BACKGROUND OF THE INVENTION The invention relates to an apparatus for electroslagremelting of metals, in particular, steel. An electrode consisting of substantially the composition of the end product is mounted in an electroslag-remelting installation. This installation comprises a water-cooled mold and a base plate mounted underneath the mold. Installations of this type are, for example, disclosed in the U.S. Pat. application Ser. No. 773,622, filed Nov. 5, 1968, which is co-assigned to the assignee of the instant application. The mold in this type of installation contains liquid slag and the electrode is immersed in this liquid slag. An electric current is passed through the electrode and causes the same to melt within the mold thereby forming within the mold liquid molten metal which solidifies within the mold and thus forms a solid metal ingot which exits from the bottom of the mold and is supported on the aforementioned base plate.

In the aforedescribed'known installation forming part of the prior art, the metal ingot which exits from the water-cooled mold comes into direct contact with the ambient atmosphere, and as a consequence of this, the metal ingot is intensely cooled at its lower end by the air, in particular, when this exposed end has acquired a substantial length. In the event the steel in question consists of a type of steel which vis sensitive to heat cracking then the strong cooling effect causes substantial cooling cracks in the metal ingot. Other types of steels, even when they are to be hot-worked immediately after the remelting process, must, due to the low temperature attained by the metal ingot due to the aforementioned cooling effect, be carefully re-heated prior to the hot-working step in order to avoid heat cracks.

SUMMARY OF THE INVENTION 'It is, therefore, a general object of this invention to provide a process and installation to avoid the aforedescribed drawbacks.

In accordance with the invention, there is provided a process for electroslag-remelting of steels, wherein the metal ingot exiting from the mold is maintained in its heated condition or is additionally heated. In the process in accordance with the invention, it is advantageous to maintain the steel ingots exiting from the mold at a temperature of at least 500C. If this minimum temperature is maintained, then even with those steels favoring segregation of metals such as, for example, nickel-, molybdenum-, and vanadium-alloyed steels, can be produced with the process of the invention while avoiding the phase segregations which cause undesirable internal tensional forces.

BRIEF DESCRIPTION OF THE DRAWING The invention is illustrated by way of example in the accompanying drawing which forms part of this application and in which:

FIG. 1 is a schematic elevational cross-sectional view of an arrangement in accordance with the invention;

FIG. 2 is a plan view of the two'ring halves illustrated in FIG. 1; and

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawing and, in particular, to FIGS. 1 and 2 thereof, there is illustrated an electrode consisting of a steel having a composition which substantially corresponds to the composition of the ingot representing the end product of the process. This electrode 10 is concentrically mounted with respect to the cylindrical walls 21 of a water-cooled mold being generally designated withthe reference numeral 20. Water or some other suitable cooling medium is adapted to flow through the hollow space defined by the walls 21 of the mold 20. The electrode 10 is adapted to have its lower end immersed into a layer of liquid slag ll floating on top ofa mass of molten metal 12 as shown in FIG. 1 of the drawing. The metal ingot 13 which is formed due to the solidification of the mol ten metal 12 within the mold comes to rest on a hori zontally disposed base plate 32 preferably consisting of copper. An electric current is passed through the electrode 10 from a source of electrical power (not illustrated) such as, for example, the secondary winding of -a transformer, through an electrical cable 30. The

other pole of the source of electric power (not illustrated) is connected via a cable 31 with the base plate 32. During the remelting process of the electrode 10, the relative height of the latter with respect to the mold 20 is continuously adjusted by cable suspension means (not illustrated) so that the electrode 10, on the one hand, is immersed with its lower end in the liquid slag 11 which floats on top of the liquid metal 12 (serving to clean and protect the molten steel) and thereby maintains the required distance between the end of the electrode 10 and the level of the molten steel 12 and, on the other hand, with the exception of the initial phase of the remelting process, the position of this level of the molten metal 12 relative to the mold 20 remains unchanged. As soon as the distance between the lower end of the mold 20 and the base plate 32 has become larger than the distance h corresponding to the height of the two-piece ring 40, then thelatter can be manually placed around the portion of the solidified ingot which extends from the mold 20 in such a way that the front faces 41 of the two-piece ring come in contact with each other. The two halves forming the two-piece ring 40 have an outer cover 42 consisting preferably of sheet metal, the cover defining a hollow space within the two-piece ring 40. This hollow space is filled with a heatinsulating material 43, for example, asbestos. In order to facilitate the manual handling of the two-piece ring 40, each half is provided with two hand grips 44 as shown in FIG. 2.

FIG. 3 illustrates an alternate embodiment of the arrangement of this invention. In this embodiment, the two-piece ring has been replaced by a plurality of pipe members 50, 50" which telescopically interact with each other. The mold 20 has a flange 22 at its lower end. Each pipe member 50, 50, 50" is provided at its lower end with a flange 53. On the top of g inner diameter of the upper pipe member 50 and thus extends over the flange 22 of the mold 22'. Each one of the lower pipe members 50, 50, 50 are provided at their upper ends with inner projections 54 which are adapted to engage the upper surfaces of the flanges 53 as shown in FIG. 3. As the mold 20' is gradually moved upwardly as the length of the ingot 13 increases, the flange 22 will abut against the lower surface of the ring 52 and thereby raise gradually the pipe member 50. A further raising of the mold 20 will eventually cause an abutting between the flange 53 of the pipe member 50 and the projection 54 of the pipe member 50, etc., thereby raising the assembly of pipe members 50, 50', 50" telescopically. At the termination of the remelting process, the innermost pipe member 50 is removed from the mold 20 by unscrewing the nuts 50' and removing the two-piece ring member 52. Thereafter the solidified ingot 13 can be removed. It can thus be noted'that during the actual remelting process, the pipe members 50, 50, 50" are raised gradually by the mold 20. As is illustrated in FIG. 3, the individual pipe members are hollow-and are filled with a heat-insulating material, for example, asbestos. As can be noted from FIG. 3, the successive pipe members 50, 50', 50" L each have a larger diameter than the preceding pipe member, thus creating in each instance a larger distance between the ingot 13 and the respective pipe member. It is also possible to provide a similar arrangement wherein the pipe member having the largest internal diameter is the one that is secured to the mold and the other successive pipe members have each a smaller diameter thereby creating a gradually smaller distance between the pipe members and the cast ingot.

As can be noted from FIGS. 1 and 3, the two-piece ring member 40 as well as the two-piece ring member 50 can be provided with electrical heating cables 45, respectively 56, which are connected to a source of electrical power (not illustrated). Thus, the ingot 13 exiting from the mold 20, respectively 20', can be additionally heated by means of the aforedescribed auxiliary heating arrangement.

Alternately, the auxiliary heating of the ingot exiting from the mold can be accomplished by means of ringshaped gas burners (not illustrated).

The process and arrangements of the present invention improve the quality of the metal ingots produced by the melting process, in particular, those metal ingots having a considerable length. Thus the process of the invention ensures the avoidance of tension cracks and also ensures the avoidance of reheating cracks without requiring an auxiliary reheating oven. in the event the steel ingots produced with the process of the invention are to be hot-worked immediately after the termination of the remelting process, the improvement provided by the invention makes it possible, due to the retention of heat energy within the ingot, to require substantially less heat energy (respectively equivalent electrical energy) to raise the ingot to the forging temperature, than comparable methods which do not use the improve ment of the arrangement and process of the invention.

at least one electrode to be fused down operatively mounted in the installation;

mold means vertically movably mounted in the installation immediately underneath said electrode and adapted to receive molten metal from said electrode extending therein which eventually forms a metal ingot in said mold means;

a base plate mounted underneath said mold means and adapted to support said metal ingot as said mold means moves upwardly relative .to said base plate;

ring-shaped heat insulating means including a plurality of ringmembers of progressively different diameters telescopically. coacting with respect to each other, the top ring member of said plurality of ring members being removably connected to said mold means.

2. An electroslag-remelting installation for remelting metal electrodes as set forth in claim 1, wherein said ring members define hollow spaces which are filled with asbestos. 

2. An electroslag-remelting installation for remelting metal electrodes as set forth in claim 1, wherein said ring members define hollow spaces which are filled with asbestos. 